The present invention relates generally to sealing components, and more particularly to the electrical bonding of components in a manner that provides for a low electrical resistance pathway between components utilizing only a localized portion of the components.
Many applications, including aerospace applications, have requirements that a low resistance pathway exist between interfacing components. This is especially true in explosive environments. These requirements are instituted to reduce the potential for an electrical short to ground between the components that could result in the generation of an electrical arc in the explosive environment.
Achieving a low resistance electrical bond provides protection for two classes of electromagnetic phenomena that can cause functional upsets in equipment, cause structural damage due to damage from concentrated energy absorption, or be potentially hazardous to personnel. Different regulatory requirements govern different equipment depending upon the application in which the equipment is used. For example, two classes of electrical bonding are applicable to composite structures; Class R and Class S. Class R electrical bonding pertains to equipment containing electrical circuits which may produce radio frequencies, either desired or undesired, and requires that the equipment be designed such that a continuous low impedance bonding path is formed from the equipment, enclosure, or housing to an aircraft structure. Class R electrical bonding also requires that this be accomplished through clean metal-to-metal, prepared metal-to-composite, or composite-to-composite contact of mounting plates, racks, brackets, or other component mating surface(s). Class S electrical bonding applies to all conductive components of an aircraft that are subject to frictional charging and do not otherwise have a bonding requirements, and states that they shall be bonded to the aircraft structure with a total path resistance of 1 ohm or less. Class R electrical bonding states that the bonding paths shall be accomplished through mechanical contact of components and shall be configured to include the minimum number of interfaces consistent with accepted design practice for that type of equipment.
Previously, one method of achieving the low resistance bonding requirement was to use the entire split line between interfacing components. A fillet of sealant was applied around the entire interface between the components and one or more bonding straps were attached to the assembled components to provide a path to ground. However, this method of achieving low resistance bonding added weight to the component assembly as a result of the sealant and fasteners used for the bonding strap(s). Additionally, the method introduced complexity into the manufacture and repair of the components as the entire interface between the components was used to achieve a solid and durable bond.